Glycerin Subs For Forage In Cattle Diets

Beef producers could reduce costs by substituting crude glycerin for a portion of the forage in growing and finishing rations, says a Texas AgriLife Research beef cattle nutritionist.

“I feel very comfortable using crude glycerin as up to 7.5% of a diet,” says Jim MacDonald.

For the past two years, he has teamed with Mike Brown, ruminant nutritionist at West Texas A&M University, to conduct four experiments on the value of adding the biodiesel byproduct to cattle diets.

“Crude glycerin is usually priced at a discount relative to corn, so we wanted to look at replacing corn to evaluate the energy value of the glycerin,” says MacDonald. “Then the question became, what if you replace forage, which would be the case with stocker cattle?”

He says glycerin has good flowability in low temperatures, as opposed to molasses and similar products, and is non-corrosive to feeding equipment – traits that make it attractive to the cattle feeding industry. Additionally, glycerin is low in phosphorus, protein and sulfur, which can be concentrated in other ration ingredients, he says.

The studies were designed to determine the feeding value, optimal concentration and dietary components that are most optimally displaced by crude glycerin in growing diets. In studies where glycerin replaced corn, the optimal inclusion was between 2.5% and 7.5%. At 10% inclusion, feed efficiency was reduced.

When forage was replaced in one study, they saw no change in average daily gain, but the cattle consumed less feed, so feed efficiency was improved. It was improved when either 5% or 10% glycerin was fed. Another advantage is a less bulky ration as forage is replaced.

The researchers even tested for a possible negative impact on fiber digestibility, but found none when the glycerin was fed at the low levels.

“We also saw an increase in microbial protein and a reduction in rumen ammonia,” MacDonald reports.

This information could lead to further studies, he says. In high-forage diets, excess nitrogen often forms in the rumen, then is excreted as urea and volatilized into the atmosphere as ammonia. The crude glycerin may allow more of the nitrogen to be captured before it’s excreted, thus reducing ammonia emissions of cattle grazing high-quality forage.

“We also observed no negative impacts on animal health from up to 10% inclusion in diets of newly received calves,” says MacDonald.